1. Field of the Invention
The present invention relates to the field of DC to DC converters.
2. Prior Art
The preferred embodiment of the present invention pertains to DC-DC buck (step-down) converters. These are switching regulators that switch one end of an inductor between the input power supply and ground. The inductor spends TON seconds connected to the input power supply and the remainder of the time connected to ground. If T is the total time for one cycle, then the output voltage (at the other end of the inductor), if filtered, will average Ton/Txc3x97VIN.
Filtering normally entails connecting a capacitor from the output side of the inductor to ground. The amount of ripple voltage at the output varies with VIN, T, L, C and VOUT.
A dual interleaved converter uses two buck converters running in parallel, but switched 180xc2x0 out of phase. Thus halfway through the first cycle of one inductor, the second inductor is switched high (to VIN). For given values of L and C, the dual interleaved converter has two advantages:
1. The ripple at the output is at least four times smaller than with the single inductor approach.
2. If designed to have the same ripple at the output, the dual-interleaved design has a response time to load changes that is at least eight times faster than the conventional design.
While dual interleaved converters are known in the prior art, such converters have not been realized in integrated circuit form because of various problems with dual interleaved converters which are not easily overcome in integrated circuit form, including but not limited to keeping inductor currents balanced.
Dual interleaved DC to DC switching circuits realizable in an integrated circuit form, capable of monitoring individual inductor current using only one current sense resistor and providing automatic duty cycle adjustment to keep the inductor currents in the interleaved DC to DC switching circuits balanced are disclosed. The preferred embodiment includes a gain error amplifier, an integral error amplifier, and a differentiator error amplifier and circuits for controlling the nominal duty cycle, with the gain error amplifier, integral error amplifier and differentiator error amplifier being adjustable independently by external components. The circuit further includes a high speed load regulation circuit that momentarily overrides the control circuitry to take over control of the interleaved converters during sudden load changes, such control also being programmable. The circuit further includes a load variation circuit to target the output voltage of the circuit to an optimal value with load to better keep the output voltage within a targeted range in the event of major step changes in the load. The disclosed embodiment is for two interleaved buck converters, though the principles of the invention are applicable to interleaved step up converters and the interleaving of more than two converters.